Combining ability of maize germaplasm is of great value to maize breeders. Thus, combining ability for grain yield and agronomic traits was studied in a line x tester crossing program. Thirty six testcrosses produced by crossing (18 inbred lines x 2 testers) along with two commercial check hybrids i.e. SC 10 and SC 128 were grown in replicated yield trail using randomized complete block design with 4 replications in 2011 at two locations, i.e. Sakha and Sids Research Stations. Data were recorded for days to 50% silking, plant and ear heights, number of ears per plant and grain yield (ard./fed.). Mean squares of entries and entries x locations exhibited highly significant to indicate that the two locations differed between them as soon as mean squares due to  lines and testers were highly significant for all studied traits, indicating the presence of wide diversity among inbred lines and among testers for these traits. The best performance and desirable GCA effects were recorded for L4 for grain yield and silking date , L14 and L18 for plant and ear heights and L3, L4 and L5 for number of ears / plant. Based on mean performance of F₁ crosses per se, cross L4 x T2 significantly out yielded the check hybrids SC 10 and SC 128. Significant positive SCA effects were found for the same single cross. The additive type of gene action played an important role in the inheritance of all studied traits except for grain yield and number of ears/plant, where non-additive gene effects played an important role in the inheritance of these traits. Moreover, the magnitude of σ²_GCAxLoc interaction was higher than σ²SCA x E interaction for all studied traits, indicating that the additive type of gene action was affected more by environment than non-additive one.